Wet processing of textiles and like materials



United States Patent 3,966,998 WET PRQCEESING 0F TEXTILES AND LilKE MATERIALS This invention relates to improvements in the technique of wet processing of textiles and the like materials. The process described herein utilizes fluidised bed.

It has been observed that the passage of wet textile fabric through fluidised beds containing solutions of dye with or without assisting chemicals (depending on the nature of the dye and the fabric) enables dyeings to be obtained which are characterised by short duration of dyeing time, better penetration and good fastness properties. It has at the same time been postulated that this result was due to the fact that the new technique (use of fluidised bed) made it possible to combine quick transfer of heat with the creation of gradients of concentration and temperature across the fibre-cross-section. (J. Sci. Ind. Res. 14B, 10, 540-42.)

According to a process already proposed, the technique used consists in the passage of the textile fabric through a fluidised bed of hot solid particles.

The purpose of using the fluidisation technique is mainly two-fold viz. (i) to bring about intimate contact of the bed particles with the flowing gases and (ii) to obtain better heat transfer rates and thermal efliciency. This technique, as applied to wet processing of textiles, is insuflicient to obtain the best results in dyeing or similar processes where diffusion or migration of dyes or similar chemicals is involved.

The essential feature of the process already proposed is a single passage of the wettened textile fabric through a hot bed of fluidised solid particles.

The object of the present invention is to achieve further improvements in the technique so that better and more eflicient dyeing or like treatment is achieved. The essential object of the present invention is to prevent excessive drying and maintain a certain minimum moisture content in the fabric so that the entire operation of dyeing or the like is carried out in an essentially moist but controlled atmosphere.

Firstly, let us take the case of dyeing itself. In the case of dyeing, there are two essential features which must be satisfied by all good dyeing techniques viz., (i) the dye particle should diffuse into the interior of the fibre cross-section to the maximum and the diffusion process to be most effective requires that a certain amount of moisture must be maintained inside the fibre during the entire period of the dyeing process, (ii) the conditions of heat application particularly at high temperatures ranging from 1l0200 C., should be such that the dye particles do not suffer decomposition or chemical degradation.

The fluidised bed dyeing technique as far as it is already known does notachieve the above conditions in case of a number of specific dyes. For example, when the operation is performed with a bed of sand of 100 Patented Dec. 4, 1962 to 200 micron particles size and cloth containing a direct dye, e.g. Chlorozol Sky Blue FF, is passed through this bed for 10 seconds at a temperature of sand of 120 C., it is found that the efiicient heat transfer conditions cause a decomposition of the dye with the resultant change of tone and dullness of the dyeing obtained. When the Caledon Red BN containing the requisite quantities of caustic and hydrosulphite is taken, it is observed that the dye penetration or diffusion is not good. It is further noticed that due to quick drying and excessive heating, the hydrosulphite in the fabric gets decomposed, resulting in specky dyeing and show ing other effects of over reduction.

Secondly, in case of alkali-scouring of cotton textiles with alkalies such as NaOH or Na CO with or without the addition of assistants such as a soap or a synthetic detergent, the normal technique of performing the operation is to saponify the oily impurities in the textile materials by subjecting them to a pressure boil (Kierboiling) for periods ranging from 6 to 12 hours. The process is therefore, an essentially cumbersome batch process. Recently continuous scouring techniques have been developed wherein the textile material is subjected to steam at to C. for periods ranging from 30 minutes to 1 /2 hours. in this case though there is improvement in the technique as compared to Kier boiling, steaming periods of the order of 30 minutes or higher entail a large size steaming chamber involving costly and elaborate steaming plants.

The use of the fluidised bed technique as already proposed in Indian specification No. 54,439 was tried and it was found that quick heat transfer followed by quick drying in 10 seconds, does not allow saponification of the oils to be effected efficiently. Higher temperatures of -200 C. in the presence of alkali also entail a danger that the textile goods may suffer alkaline degradation as it actually happens in the case of cotton textile fabrics.

Similar difficulties have also been encountered in bleaching and other processes when subjected to the technique under discussion viz., fluidised bed.

Like difliculties have been experienced in treating textiles with cross-bonding resins of the formaldehyde, glycol, amine aldehyde types.

It has been now found by intensive trials and experiments that when the object of textile treatment is to achieve some chemical or physico-chemical reaction, (in which moisture content, temperature of the fluid bed and time of contact with the bed material play an important part) it is best to modify the entire technique of application of fluidised solids to wettened textiles in a manner such that:

(a) No overheating of the fabric takes place;

(b) Complete drying of the fabric is prevented and a certain minimum of moisture is maintained in the fabric during the entire period of treatment;

(0) Advantage is taken of temperature gradient by subjecting the material to sudden heat-treatment;

(d) A longer duration of treatment under essentially moist conditions is made possible;

(e) The efficiency of heat transfer in the fluid bed is further controlled by the choice of coarser particles which have an added advantage of avoiding or minisnsasss mising the sticking of these solid particles to the Wet fabric.

These conditions are achieved by incorporating the following improvements in the technique:

(2') Firstly, a single passage of the wettened fabric is replaced by a two stage treatment consisting of a passage of the wet fabric through a fluidised bed at a relatively high temperature (110-200 C.) for a relatively short period (less than 5 seconds, preferably 1-3 seconds), followed immediately by passage through a chamber in which the fabric is heated in a gaseous atmosphere for a relatively longer period (1060 seconds) at a relatively lower temperature viz. (SO- 105 (ii) Secondly, the moisture content of the cloth as it enters the bed IOU-150% on its dry weight), the temperature of the fluidised bed 110200 C.) and the time of passage in the fluidised bed (1-3 seconds) are so adjusted that the cloth as it comes out of the fluidised bed contains a minimum of 30% moisture calculated on the dry weight of the fabric.

(iii) Thirdly, the particle size of the fluidised bed is so chosen that too eflicient a heat transfer is avoided. The range of particles is from 1090 mesh (i.e. 1600 to 160 microns); though the preferred range is 40 to 60 mesh (i.e. 350 to 250 microns).

Accordingly the present invention consists in passing the fabric successively through a fluidised bed at a high temperature (110200 C.preferably at 120-170 C.) for a short duration (below seconds, preferably between 1-3 seconds), followed by passage through a gaseous chamber, heated at a relatively low temperature (SO-105 C.) for a longer period (60 seconds).

The present invention will now be further described by reference to the following examples:

Example 1 Cotton sheeting, scoured and bleached, was passed through a 0.5% (w./v.) solution of the dye, Chrysophenine G. (Cl. No. 365) containing 0.25% (w./v.) of soda ash, kept at 80 C. It was then nipped to 100% squeeze on the dry weight of the material, and passed through the fluidised bed of hot quartz-sand particles fluidised by means of steam and maintained at 130 C. The duration of the passage of the fabric through this fluidised bed was 3 seconds. The fabric after emerging out of the fluidised bed retained about 30% moisture. It was then carried continuously into a gaseous chamber fed with steam where it stayed for another 20 seconds at 100 C. The fabric, after emerging out of the steaming chamber, was rinsed and dried in the usual manner.

Example 2 Spun rayon material, lightly scoured and dried, was

passed through a 0.5 (w./v.) solution of the dye, Chlo rozol Green EN (Cl. No. 593) kept at 80 C. it was then nipped to 110% squeeze on the dry weight of the material, and passed through fluidised bed of hot quartzsand particles, fluidised by means of steam and maintained at 130 C. The duration of the passage through the fluidised bed consisted of only 3 seconds. The fabric after emerging out of the fluidised bed retained about 30% moisture. It was then carried continuously into a steaming chamber Where is stayed for another 10 seconds at 100 C. The fabric after emerging out of the steaming chamber was rinsed and dried in the usual manner.

Example 3 Scoured and bleached cotton-sheeting was passed through a reduced dye solution (leuco) of the vat dye Cmedon Red EN 800, PB powder fine (CI. No. 1162) containing 0.25% (W./v.) of the dye, 0.05% (w./v.) ofCalsolene Oil HS, 0.725% (w./v.) of caustic soda and 1.0% (w./v.) of sodium hydrosulphite and maintained at room temperature. The fabric was then nipped to squeeze on the dry weight of the material and passed through the hot fluidised bed of quartz-sand particles, fluidised by means of steam and maintained at 140 C. The duration of the passage through the fluidised bed consisted only of 2 seconds. The fabric as it emerged out of the fluidised bed was yet relatively wet, having the moisture content of about 40% on the dry Weight or" the material, and the dye on it was still in the reduced state. It was then continuously led into the steaming chamber, maintained at 100 C., and was retained in it for about 15 seconds. The fabric after emerging out of the steaming chamber was rinsed, oxidised, scaped, washed and dried in the normal manner.

Example 4 Spun rayon material, lightly scoured and dried initially, was passed through a reduced dye solution (leuco) of the vat dye Caledon lada Green XN 2100, PD powder fine (Cl. No. 1101), containing 0.25% (w./-v.) of the dye, 0.05% (w./v.) Calsolene Oil HS, 2.2% (W./v.) caustic soda, 1.75% (W./v.) sodium hydrosulphite, 0.375 (w./v.) sodium nitrite and maintained at room tem perature. The fabric was then nipped to squeeze on the dry weight of the material and passed through the hot fluidised bed of quartz-sand particles, fluidised by steam and maintained at C. The duration of the passage through the fluidised bed consisted of only 1.5 seconds. The fabric as it emerged out of the fluidised bed was yet relatively wet, having the moisture content of about 30% on the dry weight of the material, and the dye on it was still in the reduced state. It was then continuously led into the steaming chamber, maintained at 100 C., and was retained in it for about 15 seconds. The fabric after emerging out of the steaming chamber was rinsed, oxidised, scaped, Washed and dried in the normal manner.

Example 5 A 0.25 (w./v.) dispersion of Caledon Red EN 800, FD powder fine, was prepared by using a little of Cal'solene Oil HS. Fabric, consisting of cotton poplin, was then padded with it, by passing through the dispersion so that after nipping, the fabric had 80% by Weight of the dispersion on it. The fabric was then dried, and later passed through the reducing solution containing 1% (w./v.) caustic soda, and 1% (w./v.) of sodium hydrosulphitc; nipped to 120% squeeze on the dry weight of the material and passed through the hot fluidised bed of quartz-sand particles, fluidised by means of steam and maintained at 140 C. The duration of the passage through the fluidised bed was only 5 seconds. The fabric as it emerged out of the fluidised bed still retained about 30% moisture on its dry weight, and the dye on it was in completely reduced state. It was then continuously led into the steaming chamber, maintained at 100 C., retention time here being about 20 seconds. The fabric after emerging out of the steaming chamber was rinsed, oxidised, scraped, washed and dried in the usual manners.

In all the above cases (Examples 15), the dyeing obtained was uniform, full without any speckiness, and compared well with the normally dyed sample in all respects of fastness properties. The peneration of the dye-particles inside the fabric and across the fibre cross-section was satisfactory.

Example 6 Cotton sheeting, previously desized, alkali boiled, soured etc., was padded with the solution, containing 1.0% (w./v.) sodium chlorite and 0.1% (w./v.) Lionil ART (wetting agent), maintained at 80 C. and pH=4. After nipping the fabric to 120% squeeze on its dry weight, it was passed through a hot fluidised bed of quartz-sand particles, fluidised by means of steam and maintained at C. The duration of the passage through the fluidised bed was 3 seconds. The moisture content of the material as it emerged out of the fluidised bed was about 35% on the dry weight. It was then continuously led into the steaming chamber maintained at 100 C. and was retained there for about 30 seconds. Later it was rinsed, washed etc., in the usual manner. A good bleach was obtained.

Results obtained when padding liquor consisted of:

(a) Hydrogen peroxide l-volumes), pH=10.5 and temperature 80 C.

(b) Sodium hypochlorite (3 g./1it. available chlorine), pH=10.5 and temperature cold, were similar to the one above.

Example 7 Thick woolen serge was passed through a solution of sodium hypochlorite (7 g./lit. available chlorine, ph=l0.7) and nipped to 100% squeeze on the dry weight of the material. It was then led, within 2 seconds through the hot fluidised bed of quartz-sand particles, fluidised by means of air and maintained at 140 C. The fabric at this stage was considerably wet and contained about 40% moisture. It was then continuously led through the gaseous chamber maintained at 100 C. by means of hot air, for 10 seconds. The cloth was then rinsed, antichlored, washed etc., in the usual manner.

Felting shrinkage of such a treated cloth was reduced from to only 8.0%. There was no damage to the cloth, the treatment was uniform, handle unimpaired and no loss in tensile strength.

The invention will now be further described with the help of the accompanying drawing giving diagrammatic sketch of the apparatus.

Referring to the drawing, fabric 2 is wetted with the dye liquor (or any other treating solution) contained in the treating bath 1 and the excess liquor removed by a pair of nipping rollers 3, after which it enters the fluidised bed 4, containing discrete solid particles e.g., sand (quartz), glass beads or porcelain beads of 80 mesh size, held at 120-170 C. by means of hot air or superheated steam, distributed evenly through the plate 9. The fabric is guided through the fluidised bed by a set of guide rollers '7 and a set of bottom rollers 6. As it emerges out of the fluidised bed 4, the adhering particles are brushed off at the exit end by a pair of rotating brushes 8, after which it leaves the fluidised bed and continuously enters gaseous chamber 1d which carries the set of guide rollers 15, kept at relatively lower temperature (80l05 C). A set of driving rollers 13 draw the fabric out of the second chamber 10, to be collected later by collecting mechanism 14. "12 is a valve which connects the jacket 5 of fiui ised bed chamber t with the jacket 11. of the second chamber 10.

The speed of the machine and the height of the fluidised bed are so chosen that the time of the fabric inside the fluidised bed is less than 5 seconds (preferably l3 seconds), and that inside the gaseous chamber 1%, is about 104:0 seconds.

The treating bath 1. is so constructed that it holds the minimum quantity of liquor yet allows sufficient time of contact for the material with the treating liquor. It is provided with thermostatically controlled heating arrangement, adequate circulating system and sampling arrangement.

Bottom rollers 6, are provided with steam injection arrangement, such that the bearings and the bush are protected from sand. These rollers which are mounted on hollow shafts are themselves perforated so that a part of the fiuidising medium can be fed through the shaft and along the periphery of the rollers to the solid particles lying above these rollers and between the folds of the fabric.

External heating jacket 5, around the part of the fluidised bed chamber 4, helps to keep the fluidised bed at the requisite temperature, while the heating-medium which may be hot air, steam etc., after passing through this jacket enters the external jacket 1.1, of the gaseous chamber 10, and finally enters the chamberlll at the bottom. The fluidised bed 4- can also be provided with an automatic threading device (not shown in the figure).

Having now particularly described and ascertained the nature of our said invention and in what. manner the same is to be performed, we declare that what we claim l. A process for the diffusion of a treating chemical in aqueous solution or dispersion into the fibres of elongated textile material, which comprises, after impregnating the textile material with an aqueous treating liquid containing said chemical, continuously passing the impregnated material while still wet with said liquid through a bed of discrete solid particles maintained in a fluidized state and at a temperature between 110 and 200 C. and removing the material from the fluidized bed after a contact period therein of only 1 to 5 seconds, thereby raising the temperature of the material abruptly for diffusion of said chemical into the fibres of the material and yet keeping the material in a moist condition, and then passing the material while it is still moist with said liquid through a treatment chamber containing a gaseous heating medium at a temperature lower than that of the fluidized bed and in the range of about to 105 C. and retaining the material in said heating medium for a period of about 10 to 60 seconds, thereby bringing about the desired ditfusion of the treating chemical into said fibres.

2. The process of claim 1 wherein said solid particles are of between 1600 and 160 microns in size.

3. The process of claim 1 wherein said solid particles are of between 350 and 250 microns in size.

4. The process of claim 1 wherein said solid particles are particles of a substance selected from the class con sisting of sand, glass and porcelain.

5. A process for the difiusion of a treating chemical in aqueous solution or dispersion into the fibres of elongated textile material, which comprises, after impregnating the textile material with an aqueous treating liquid containing said chemical, continuously passing the impregnated material at a moisture content of about to 150%, based on its dry weight, through a bed of discrete solid particles of from 1600 to 160 microns in size while maintaining said particles in a fluidized state and at a temperature between ll0 and 200 C. by flowin a heated, gaseous fluidizing medium through said bed, and removing the material from the fluidized bed after a contact period therein of only 1 to 5 seconds, thereby raising the temperature of the material abruptly for diffusion of said chemical into the fibres of the material and yet keeping at least about 30% of moisture in the material while it still contains said moisture, and then passing the material through a treatment chamber containing a gaseous heating medium at a temperature lower than that of the fluidized bed and in the range of 80 to C. and retaining the material in said heating medium for a period of 10 to 60 seconds, thereby bringing about the desired difiusion of the treating chemical into said fibres.

6. The process of claim 5 wherein said particles are particles of from 350 to 250 microns in size of a substance selected from the class consisting of sand, glass and porcelain.

7. The process of claim 5 wherein said fluidized medium is superheated steam.

8. The process of claim 5 wherein said heating medium is steam.

9. A process for the diffusion of a dye in aqueous solution or dispersion into the fibres of elongated textile material, which comprises, after impregnating the textile material with an aqueous dye liquor, continuously passing the impregnated material at a moisture content of about 100 to based on its dry weight, through a bed of discrete solid particles of from 1600 to microns in size while maintaining said particles in a fluidized state and at a temperature between 120 and 170 C. by flowing superheated steam through the bed, and removing the material from the fluidized bed after a contact period therein of only 1 to 5 seconds, thereby raising the temperature of the material abruptly for diffusion of the dye into the fibres of the material and yet keeping at least about 30% of moisture in the the material while it still contains said moisture, and then passing the material into a steaming chamber maintained at a temperature lower than that of the fluidized bed and in the range of 80 to 105 C. and retaining the material in said chamber for a period of 10 to 60 seconds, thereby bringing about the desired diffusion of the dye into said fibres.

References (Iited in the file of this patent UNITED STATES PATENTS 2,424,857 Scull July 29, 1947 2,533,248 Helmus Dec. 12, 1950 2,537,290 Williams et a1 Ian. 9, 1951 2,664,009 Emerson Dec. 29, 1953 2,664,010 Emerson Dec. 29, 1953 2,693,995 Hannay et a1 Nov. 9, 1954 2,785,478 Audas et al Mar. 19, 1957 2,901,3l2 Audas et al Aug. 25, 1959 2,964,852 Doleman et a1. Dec. 20, 1960 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3 O66 998 December 4, 1962 Vasant Ba Chipalkatti et al.,

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 46, for "object" read objective column 3, line 65, for "15 read it column 4, lines 13 and 35, for "scapedfl, each occurrence read soaped line 57 for "scraped" read soaped line 62, for "peneration" read penetration column 6, line 60, for "fluidized" read fluidizing Signed and sealed this 10th day of September 1963v (SEAL) Attest:

ERNEST w, SWIDER DAVID LADD Attesting Officer Commissioner of Patents 

1. A PROCESS FOR THE DIFFUSION OF A TREATING CHEMICAL IN AQUEOUS SOLUTION OR DISPERSION INTO THE FIBERS OF ELONGATED TEXTILE MATERIAL, WHICH COMPRISES, AFTER IMPREGNATING THE TEXTILE MATERIAL WHICH AN AQUEOUS TREATING LIQUID CONTAINING SAID CHEMICAL, CONTINUOUSLY PASSING THE IMPREGNATED MATERIAL WHILE STILL WET SAID LIQUID THROUGH A BED OF DISCRETE SOLID PARTICLES MAINTAINED IN A FLUIDIZED STATE AND AT A TEMPERATURE BETWEEN 110 AND 200*C. AND REMOVING THE MATERIAL FROM THE FLUIDIZED BED AFTER A CONTACT PERIOD THEREIN OF ONLY 1 TO 5 SECONDS, THEREBY RAISING THE TEMPERATURE OF THE MATERIAL ABRUPTLY FOR DIFFUSION OF SAID CHEMICAL INTO THE FIBRES OF THE MATERIAL AND YET KEEPING THE MATERIAL IN A MOIST CONDITION, AND THEN PASSING THE MATERIAL WHILE IT IS STILL MOST WITH SAID LIQUID THROUGH A TREATMENT CHAMBER CONTAINING A GASEOUS HEATING MEDIUM AT A TEMPERATURE LOWER THAN THAT OF THE FLUIDIZED 